Process of producing ammonia from alkali cyanid.



c. F. BIERBAUER L. s. FINCH. PHUCESS 0F PRGDUCNG AMMNIA FROM ALKALICYANILD.

APPLICATIDN FILED .IUIQY 23,1918. 1,295,262. Patented Feb.25,1919.

fcaffti. F. BI'EaBaUEa, or iii-invit, AND Laon s. einen, or novna, NawJERSEY,

AssIGNoias rro HERCULES POWDER coiurfiivv, or WILMINGTON, nicnawaan; a;

CORPORATION OF DELAWARE.

EROCESS OF PRODUCING AMMONIA. FROM ALI CYANIB.

To all whom it may concern:

Be it known that we, CARL F. BIERBAUER and. LEON S." FINCH, citizens ofthe United States, residing, respectively, at Kenvil and Dover, countyof Morris, and State of New "Jersey, have invented a new and usefulImprovement in Processes of Producing Ammonia from Alkali Cyanid, ofwhich the --following is a full, clear, and exact description, referencebeing had to the accompany- .ing drawings, which form a part of thisspecification.

This invention relates to the hydrolysis of alkali metal cyaiiids intoammonia and other compounds. The invention is applicable to theproduction of ammonia from cyanid prolduced 'by passing nitrogen over -amixture of "1 an* alkali `or alkaline earth metall compound (such assodium carbonate) and carbon, or v carbonand finely divided iron, toform a cyanid of the alkali metal used. This l`method is old and wellknown and has been successfully practised and even commercia'lly rusedin Europe.

The process, however. has notgone into general use, largely because ofthe practical difficulties encountered in the""attemp't to secure agoodv yield 1 of ammonia from `'the cyanid.

is well knownthat when cyanids are subjected to the action of steam at arelatively high temperature ammonia is formed.

With sodium cyanid, the equation would be:

(i), Nacummojzi-icozuaaruir ,""lVhere', however,I the product of thecyanid-forming reaction contains carbon, iron,

4 sodium feri'ofcyaiiid, sodium hydrate and sodi'u'in" carbonate, thesimple method of distilliiig' witli` steam, orthe rather obviousexpedient of adding water and heating. under pressure in an autoclave,gives compara- "tively Ipoor results( Nor are the difficulties Ymorethan partly overcome by the removal "of the insoluble materials (carbonand'iron) an inexpen .duction or f bytk not" v li'ngixitec y lducedbyanyxparticular processfand is even applicableto pure cyanids.

lVhile the processie not dependent for its execution upon any particularapparatus, it is preferred to carry out the -process in an apparatusconstructed substantially in accordance with the accompanying drawings,wherein Fig'ures 1 and 2 are diagrammatic views showing two parts ofthe" apparatus.

The cyanized material, which may contain sodium cyanid, sodium hydrate,small quantities of sodium ferro-cyanid, sodium carbonate and sodiumsulfate, and insoluble substances, which may be Icarbon and iron, orcarbon alone, is preferably first cooled in an atmosphere of nitro-gen.One part of the powdered cyanized material is blown into a spray of oneto three parts of water or'weak liquor. a represents the water orweakliquor-storage tank, b the spray-head connected by pipes with tanka, d the feed' for the dry powder, and e the mixer, oii the top of whichthe dry powder feed and the sprayhead are mounted. The bottom of themixer e opens into one end of an agitator, consisting of a' narrowhorizontal cylinder or chamber f through 'which extends longitudinally ascrew conveyer g provided with beaters h. The outlet of the agitatorcommunicates with a filter z'. This filter is preferablyvof the rotarycontinuous type, and is well known in the art, and its construction neednot, therefore, be described.

` If the cyanized material contains iron, which it will if iron is usedas the cata-lytic agent in the preparation of the cyanized material, theformation of sodium ferrocyanid proceeds upon vthe mixture of thematerial with watei. In the preferred way of carrying out the process,it is desirable to avoid the formation of sodium ferro-cyanid insubstantial quantities, as' the hydrolysis: of sodium ferio-cyanid'toammonia is more diiicult than is the hydrolysis of sodium cyanid toammonia. By the use of the colit-inuous dissolving or mixing apparatusdescribed, vfollowed by rapid filtration, which can be effectedifn ya-rcontinuous rotary filter,

the time that the aqueous cyanid Solution is in contact with the finelydivided iron may be cut to a minimum, and if the original cyanid mixture`is comparatively free 'of fer'ro-cyanid, very little"'ferio=cyani'dwill pass out of the filter. v

The strong sodium cyaiiid solution ob- Specication of Letters Patent.Patmte Fgb, 21', llp- Application filed July 23, 1918. Serial No.246,279. i

'tained from the filtration passes, through a pipe a', to a still j,whichmay be maintained about half-filled'. -,Within the still,preferably the lower part, are steam coils le, which at oneend areconnected with steam inlet pipes m and at the other end with steam trapsn. There is also a steam pipe o entering the interior of the still,whichl provides i an efficient way to rapidly heat the contents of thestill when .the solution 'becomes -too concentrated. The pipe o Shouldextend beneath the surface of the cyanid solution. l

At the top of the still is a; pressure relief valve p which controls thepassage of the distillate to a trap tankr. i The trap 1' -is l alsoconnected with a reflux condenser s which may be a1rcooled, but which ispreflerably water-cooled. The condense-r s is con- 'nected with anordinary water-cooled condenser t, which is tipped downward so as todrain into a neutralizing tub (not shown).

Steam 'a't 125 pounds pressure may be conveniently used, although thesteam pressure may be as low as 50 pounds or even lower. A pressurehigher than lpounds .is practicable, but in the preferred process it isunnecessary. Similar autoclave processes usually require superheatedsteam, or steam above 125 pounds'pressure. If the solution in the stillis too concentrated, it is advisable Y to admit steam direct into thestill, thereby exceeded.

more rapidly heating the contents and a'tthe same time reducingthe'concentration. When the solution is of the concentration desired,steam should be admitted solely to the steam coils.

The higher the pressure within the still',`

l the more rapid is the hydrolysis; Itis found desirable to set therelief valve to open only when the pressure exceeds approximately- Yfifty pounds to the square'inch. Hydrolysis of solutions of'sodiumcyanidv of varying concentration takes place readily at a pres-Asureofthirty pounds to the square inch, or

evenl at 'a lower pressure. The pressuregof fifty pounds to the squareinch may be safely The pressure of the steam and the pressure maintainedwithin the .tank may be varied within rather wide limits, dependent uponthe composition of the' solution, its concentration and the desired rateof distilllation. For commercial operation, steam at 125 pounds pressureand a pressure within the tank of 50 pounds are preferred. Substantialuniformity of pressure, which'is secured by means of-the relief valve,is of im-l portance, and seems to benecessaryin order that the processshall operate efficiently and without mechanical trouble. lThedistillate'- (steam and-'ammonia) escaping at the relief valve passes tothe trap tank r and thence to the'reflux. (preferably 'water-cooled)condenser s." Nearly al1 the moisture which escapes with the ammonia iscondensed in vthe condenser s and returns to the trap tank. The ammoniawhich passes on through the condenser s iscooled by passe ing throughthe water-cooled condenser t, which drains into the neutralizing tirbabove mentioned.

At the start of the run gaseous ammonia is produced andat the end of therun aqueous ammonia.4 It is not especially sought,

however, to produce gaseous ammonia, but strong ammonia solution, sothat Vthe subsequent neutralized liquor will require as littleAevaporation aspossible. .Hence, vall distillate which collects incondenser 't is altions are the same. v The aqueous ammonia whichcollects in thetrap tank 1" is much weaker than that which passes intothe neutralizing -tu-b. This weak distillate may be utilized as such, orit may bev pumped back into the hydrolizing still and redistilled,giving a strong ammonia.

, The pumping backinto the still of this weak aqueousammonia is alsoadvantageous in thatthe liquor 'in the still is prevented from reachingtoo high a concentration.

The sludge left in the still may be drawn oli' through a valv-e gatewand is 'used in the manufacture of moresodium cyanid, or for theproduction of formate compounds.

By the process described, from"60 to f95 per cent. of thethbreticalammonia distils off 'during the. iirsthour. At endof less than fourhours practically 100-per cent. of the"tlieoretical4 ammonia isldistilled off.

' These Qfresults are attained with av`4 full sized apparatus operatingon a commercial scale.

.The rate Aat which the ammonia, distils'oif' will depend upon the sizeandcon'struction iio of the'lap'paratus, the temperature and presthetank.

The solution of sodium cyanid should contain lat least enough water tosatisfy the equation given at vthel beginning ofthis specification.While actual practicedenionstrates the success of the process as appliedto sodium cyanid containing the impurities specified herein', it isbelieved that the process will operate v,equally well where otherimpurities are present as the result of producing the cyanid byprocesses other than that herein mentioned. Impurities do not;

apparently affect the reaction. Nor 'is the Ysurefalnd the concentrationof the .liquor 'in' incassa process limited to a cyanid produced fromsodium carbonate. However, no substantial proportion of any sodiumferro-cyanid that is contained in the solution can apparently.

Y 4required for the treatment of sodium cyanid (although the treatmentsoboth have important features in common), it may be desirable, if theoriginal cyanid mixture is composed largely of ferro-cyanid, to hydro-,lyze the solution under steam pressure conditions adapted to thetreatment of ferrocyanid. In an application filed of even date herewith,Serial No. 246,360 theproduction of ammonia from alkali metalferro-cyanid, and the preliminary production of alkali metalferro-cyanid from alkali metal cyanid or a mixture of alkali metalcyanid and alkali metal ferro-cyanid, are specifically described andclaimed.

While thecyanid herein described 'is pref- .erably produced from sodiumcarbonate, because of its cheapness and availability, the cyanid may rbemade from other alkali or alkaline earth lmetal compounds. Generallyspeaking, the process is applicable to anycyanogen .compound of anyalkali or y alkali earth metal, whether pure or impure,

rit being understood that in the known processes for producing cyanid,Iespecially those in which -an'alkali-Inetal salt and carbon, witherwithout the addition of finely -divided iron, are acted upon bynitrogen,

the presence of impurities corresponding to those hereinbe'forementionechis unavoidable. One of the advantages of vthe process is thatit is not essential, on the one hand, to'purify the solution resultingfrom leaching the material from the urnaces,`nor on the other hand, tomake any additions to the leached solution. In view of the fact that theprincipal features of the` process herein described are common` to thetreatment of both valkali metal cyanid and alkali metal ferro-cyanid,and that in the' treatment of alkali .metal ferro-cyanid the sameprocess is used as herein described' but modified by features.ofindependent novelty, it is not intended ftion is generic,'as well asspecied to the hydrolysis of ammonia from cyanid, the

hydrolysis to ammonia of alkali metal ferro-cyanid being in the natureof a speciic improvement lon the generic invention.

Having. now fully described our invention, what we claim and desire toprotect by Letters Patent is:

1. The process of producing ammonia from a solution of alkali metalcyanid which comlprises distilling o' the ammonia by heat whilemaintaining the solution under a substantially constant pressure.

2. The process of producing Iammonia from a solution of alkali metalcyanid which comprises subjecting the .solution to heat and pressurewithin a confined still and providing for the intermittent escape ofthedistillate whenever the pressure reaches a predetermined maximum.

3. The process ofproducing ammonia from a solution of alkali metalcyanidwhichk comprises heating the solution both by direct injection of steamand by exterior application of heat. 1 i

4. The process of producing ammonia from a solution ofalkali'lmetalicyanid which comprises subjecting the, solution to heatand pressure to distil off ammonia and water vapor, and condensing outwater vapor from the distillate and retui ning it to the still, therebypreventing the solution under going distillation from reaching too higha concentration. v

5. The process of producing ammonia from a solution of alkali metalcyanid which comprises distil'ling off the ammonia by 100 heat,maintaining the solution under a substantially constant pressure andadding water to-the solution during distillation.

6. The process of producing ammonia from a solution of alkali metalcyanid which 105 .comprises distilling oil' ammonia and water vaporWhile maintaining the solution u'nder aslrbstanti'ally constantpressure, condensing out water vapor from the distillate, and returningthe condensed vapor to the so- 110 lution.

7. The process of producing ammonia from-a solution of alkali metalcyanid which .comprises distilling oft' ammonia and water vapor, and-subjectingfthe distillate to a plu- 115 rality of successiveeondensations at progressively decreasing temperatures.

, 8. The process of producing ammonia from a solution of alkali metalcyanid which comprises distilling off ammonia and water 120 vaporwhile'maintaining the solution under a substantially constant pressure,condensing out Water-vapor from the distillate, returning thec'ondensed'vapor to the solution,

and subjecting the uncondensed distillate to 125 further condensation. v

9. The process of producingA ammonia from a solution of alkali metalcyanid which`4 comprises subjecting the solution to heat and pressure todistil .oil1 ammonia "and 180 Water vapor, .condensing out Water vapor sfrom the distillate and allowing it to accu mulate, and intermittentlyreturning portions -of'the accumulated condensed Water vapor to the body`of tlie solutiongunder going distillation. 'l i a 10. The process' ofproducing ammonia from a mixtureof alkali; metal cyanid and t. materialinsoluble in Water,. Which consists in adding a liquor.' consisting'Wholly orv mainly of Waterto the mixture, mixing and agitating,removing the insoluble material from the solutiom and distillingv oEjtheammonia by heat and-pressure. j 11.'The process of producing ammoniafrom a mixture yor alkali metal cyanid and material Ainsoluble invWater, which consists in .adding a liquor consisting Wholly 4or mainlyof water to the mixture, mixing' and agitating5 removing the insolublemav'teii'al from thev solution, andl distilling'v off the ammonia fromthe solution -by .heat L While maintaining the solution under a A'b-LAstantially constant pressure. I

12. The process of producing amm nia 'from-a mixture of alkali metalcyanid, iron and carbon; which consists-in adding to the mixturea liquorconsisting Wholly or mainly of Waterland immediatel agitating and re-'moving the iron and car on from the solution by quick filtrationbeforeany substanv tial part of the iron reacts to form any sub-.stantia-l quantity of ferro-cyanid, and then hydrolyzi-ng to ammonia,-the hydrolysis being effected by heat'while maintaining thesolutionunder a substantially constant prescyanid mixture into a sprayof water, agitating, continuouslyvflteringto Separate the insolublematerial from the cyanid solution,

v{and distilling ofi' the ammonia by heat Whilev maintaining thesolution under a substantially constant pressure.

met-al cyanid solution for distilling oif ammonia, which consists inadding to' a niix-4 ture of alkali metal cyanid and material insolublein Water a liquor consisting Wholly or mainly of Water, mixing andagitating, and removing the insoluble material -froin the solution. f

15. The process of preparing an alkali metal -cyanid solution fordistilling-oii ammonia which consists 'in addin'glto a mixture of alkalimetal cyanid and material in'- soluble in Water a liquor consistingwholly ormainly ofwater, mixing and agitating,

passing the solution through a filtering med-ium, passing Water throughthe filtering .medium to remove anyijsolu'ble salts adhering thereto,and utilizing the resultant Wea-k cyanid solution in mixing andagitating With subsequent mixtures of cyanid and insoluble material.-

-16. The process of preparing an alkali metal cyanid solution fordistilling off ammonia, from a mixture offalkali metal cyanid, iron andcarbon, which consists in adding to the mixture a liquor consistingwholly or .mainly of Water and immediately agitating and removing theiron andlcarbon from the solution 'by quick filtration before anysubstantial part of Vthe iron reacts with the mixture to form anysubstantial quantity of ferro-cyanid.

17. The process of preparing anl alkali metal cyanid solution fordistilling ofifammoniafrom a mixture of alkali metal cyanid, iron andcarbon, which consists in blowing the cyanid. mixture into a spray ofwvater, agitating2 and continuously filtering to separatesthe insolublematerial from the cyanid solution;

In testimonyof1 which invention, We have hereunto setpour hands atKenvil, NeWJer-v sey, on this 19th day `of July, 1918.

CARL r. BIERBAUER. LEON sfriucii.` a

